The invention relates to landing gear particularly for raising or lowering a trailer or other load-transporting vehicle provided with landing gear comprising two support legs and two pressure fluid cylinders, wherein each support leg is formed of an elongate member attached at its first end pivotally to the trailer chassis, and where in between each support member and the chassis there is fitted a cylinder, so that the support member can be turned by means of the cylinder.

In the prior art there are known many different types of hydraulic landing gear for trailers, for example as illustrated in the Brittish publications GB 1,098,510 and GB-A 2,109,322, as well as in the American patent publication US 3,874,696.

The Brittish patent publication GB 1,098,510 introduces turnable support posts to be employed particularly in connection with semi-trailers, hitch-ups and the like. The support posts are attached at the front end of the trailer, and they are lowered down and locked in the supporting position when the tractor is desired to be disconnected from the trailer. The support posts are interconnected by means of a transversal support member, and the piston rod of the hydraulic cylinder is coupled in the middle thereof. One end of the cylinder is attached to the trailer. The support posts are provided with telescopic ^' struts, and these include locking means whereby the struts and the posts can be locked in position. The cylinder is operated by a manual pump. The support struts can also be mechanically extended by a hand lever.

A major drawback in the above described support posts is the fact that they are not suitable for raising and/or lowering trailers: when the support posts are adjusted to their load-bearing position, the trailer

is lowered to rest upon them, so that the tractor can be disconnected from the trailer and again easily reconnected thereto. The support posts are light in construction, and they are not suited for carrying heavy loads.

The Brittish patent application GB 2,109,322 introduces hydraulic support leg mechanisms for caravans or the like, whereby a parked caravan can be levelled to the horizontal position. The disclosed support legs, turnable by means of hydraulic cylinders, are not structurally suitable for raising the caravan, and it Is not even suggested; the caravan rests on its own bogle.

The US patent publication 3,874,696 introduces a landing gear arrangement for trailers. The described arrangement corresponds to the landing gear structure disclosed in the Brittish patent application GB 1,098,510. These suggestions for landing gear can neither be employed for raising and/or lowering a trailer. Another landing gear arrangement is schematically Illustrated in the US patent publication 4,413,943. A pair of legs is installed in between the wheels of the rear bogie of a trailer. These legs can be hydraulically raised and lowered so that the rear end of the trailer can, by means of the legs, be supported against the ground. The drawback of this landing gear arrangement is the relatively troublesome two-step operation of the legs. First the support legs are extended out of the trailer chassis and then down along the ground, when they are not needed. Moreover, the said landing gear arrangement may obstruct the shifting of the trailer bogie, when it is used in connection with trailers provided with a movable rear bogie.

The object of the present invention is, among other things, to eliminate the above mentioned drawbacks and to provide a simple and easily adjustable landing gear arrangement. This s achieved by the

characteristic novel features of the nvention, enlisted in the appended patent claims.

Among the advantages of the landing gear according to the present invention, let us mention that the loading and unloading heights of the trailer do not cause any problems. Irrespective of the load, the rear end of the trailer can be lifted to the desired height or lowered to the ground level. The trailer can be moved, resting on this landing gear which is adjusted to the desired height, if the support legs are provided with wheels. According to the invention, the height of the rear end of the trailer can be steplessly adjusted by means of the landing gear, and the landing gear can be charged with a full load in any of its adjustable positions. Moreover, each pair of support leg and cylinder can, if necessary, be adjusted irrespective of the other. The adjusting of the cylinders can be controlled for instance from the tractor.

The landing gear of the present invention is particularly well suited to be used in connection with trailers and the like provided with a movable bogle. In its non-operative position, the landing gear does not disturb other operations dealing with the trailer, such as shifting or installing the bogies. In addition to this, the landing gear can be placed in the trailer chassis, in the vicinity of. the locking spot of the bogie, and even totally or partly above it. The track gauge of the wheels possibly provided in the support legs of the landing gear can then be the same as the track gauge of the bogie wheels. This is the case for instance when the invention is applied to a railway car or a similar car moving on rails.

In the following the invention and its other advantages are explained in detail with reference to the appended drawings, where figure 1 is a side-view illustration of the rear end of a semi-trailer, with the landing gear of

the present invention attached thereto; and figure 2 respectively illustrates the rear end of a semi-trailer, seen from the top.

The landing gear 1 of the present invention comprises two support legs 4 and two pressure fluid cylinders 5. They are placed in the rear end of the trailer 2, in the vicinity of the rear bogie 3 or a similar rear wheel arrangement, in this case on both sides thereof. The trailer complete with the rear bogie is for instance similar to the one described in the US patent publication 4,413,943. The landing gear of the present invention is well suited to be used in connection with this kind of trailers or semi-trailers. Each support leg 4 is formed of an elongate member which at its first end 4a is pivotally attached to the chassis 7 of the trailer 3. In between each support leg 4 and the chassis 7, there is fitted a pressure fluid cylinder 5 so that the support leg is turnable by means of the cylinder. Each pair of support leg and pressure fluid cylinder 4, 5 is at its first end 4a, 5a pivotally attached to the rear of the trailer 2, in connection with the chassis 7 proper, in this case to the sides, in between the rear bar 14 and the cross bar 15, or in between corresponding members of the chassis 7, such as sideways protruding members. In addition to this, the support leg 4 and the pressure fluid cylinder 5 are attached, in the longitudinal direction of the trailer 2, at the distance a from each other. The second end 5b of the cylinder 5 is pivotally engaged to the second end 4b of the support leg 4, or to the vicinity thereof. The length of the cylinder 5, with the piston retracted, and the length of the support leg 4, roughly corresponds to the mutual distance a of the fastening points of the first ends 4a, 5a thereof.

In that end of the support leg 4 which is to be placed against the ground, there is installed a

support member, either a suitable shoe or, as in figures 1 and 2, a wheel arrangement 8. The second end 5b of the cylinder 5, i.e. the end of the piston 6, is attaced to the center of the support member and at the same time to above the central line A-A, seen from the side of the support leg 4, when the support legs 4 are retracted (indicated with dotted lines in figure 1). Now the support leg 4 is sure to start turning down, towards the ground, when pressure fluid is conducted into the cylinder 5.

The support leg 4 is advantageously provided with the wheel arrangement 8. This may be similar to the one illustrated in figures 1 and 2, or some different arrangement, for example a one-wheel modi ication. In this case the wheel arrangement 8 of each support leg 4 comprises two wheels 9, 10, which are interconnected by means of an axis 11, or a corresponding coupling means. The axis 11 is attached to the bottom end of the support leg 4, advantageously on its center line A-A. Above it, there is in turn attached the head of the piston 6 of the cylinder 5 by means of a pin 12 or the like.

If necessary, the support leg 4 can be realized as a box-type girder, either hollow or open on one side. In that case in connection thereof, advantageously inside it, there can be arranged another support leg in the longitudinal direction thereof, for example a continuation for the support leg 4, and/or a pressure fluid cylinder 13. The cylinder 13 is attached to the support leg 4, and its other end 13b Is attached to the continuation of the support leg 4, or directly to the support member provided at the end of the support leg, such as the axis 11 of the pair of wheels 9, 10. By means of the second cylinder 13, the support leg 4 can, when necessary, be extended. It is pointed out that when the head of the piston 6 of the cylinder 5 is attached to the wheel arrangement 8 or the like, whereto

the continuation of the support leg 4 or the cylinder 13 is likewise attached, the resulting structure is a highly stable and efficient landing gear arrangement. The pairs of support leg and pressure fluid cylinder 4, 5 included in the landing gear of the invention are attached to the sides of the chassis proper 7 of the trailer 2. Therefore the transversal rear bar 12 of the trailer 2 is somewhat extended, and the cross bar 15 is installed at the distance a therefrom. Alternatively, in connection with the chassis 7 there can be provided suitable protruding members or other support pieces, in between which the pairs of support leg and cylinder 4, 5 are fitted. The first ends of the support leg 4 and the cylinder 5 are pivotally attached to the above mentioned bars 14, 15.

In between these, and to the outside with respect to the chassis 7, there can be provided a suitable safety bar 16 or the like. The pairs of support leg and cylinder 4, 5 can, if desired, also be protected by means of a suitable casing, in which they can be retracted in the inoperative position.

The support legs 4 of the landing gear of the invention are at least roughly parallel to the axis B-B of the chassis 7 when in retracted position, as is illustrated by the dotted lines in figure 1. Thus they do not disturb the normal operation of the trailer, or the moving of the bogies, and the access to the vicinity of the rear bogie of the trailer - for maintenance and other possible purposes - stays ree. Moreover, the movable rear bogie 3 can also be located even directly below the support leg. When the rear bogie 3 is drawn to the front end of the trailer, for instance in the fashion described in the US patent publication 4,413,943, or it is simply desired to be lifted off from beneath the trailer (for instance to be replaced by another bogie), pressure fluid is conducted to the cylinders 5 of the landing gear 1, so that they start to

turn downwards with respect to the level of the chassis 7. When the support legs 4 rest securely against the ground, the supply of pressure fluid into the cylinders 5 is stopped, whereafter the rear bogie 3 can be driven to the front end of the trailer. If the landing gear is located above the locking spot at the rear of the rear bogle, the rear bogle 3 is - before the support legs 4 are turned from the rest position to against the ground - moved somewhat towards the front end of the trailer and then stopped, whereafter the support legs 4 are pressed, by means of the cylinders 5, against the ground or other base, in the fashion described above. By means of the landing gear of the invention, the rear end of the trailer can be lifted even higher than it is when resting on the rear bogie. On the other hand, the rear end of the trailer can be lowered near to the ground level and still, if the support legs 4 are provided with wheels 8, be transported from one place to another drawn by the tractor. In the above description the invention has been explained mainly with reference to one preferred embodiment only, but it is naturally clear that the invention can be modified in many was within the scope of the appended patent claims. Thus for instance the support leg 4 and the cylinder 5 can be connected to the supporting member, such as the wheel arrangement 8, also in some other fashion than the eccentric one described above; they can be coupled to the same axis 11 or the like, if in the retracted position the topside angle between the support leg 4 and the cylinder 5 is less than 180 . This can be arranged for Instance by means of some suitable stationary obstacles or the like provided in the chassis. It is also pointed out that the landing gear of the invention can be applied, apart from the semi-trailer suggested in the preferred embodiment described above, also to some other kind of load-transporting vehicle, such as a railway car or a

similar vehicle provided with one or several wheel bogies and transported along the ground or along a track.